An Unexpected Reversal of Diastereoselectivity in the [4+3]-Cycloaddition Reaction of Nitrogen-Stabilized Oxyallyl Cations with Methyl 2-Furoate
作者:Richard Hsung、Jennifer Antoline
DOI:10.1055/s-2008-1042765
日期:——
An unexpected reversal of diastereoselectivity in the [4+3] cycloaddition of methyl 2-fuorate with nitrogen-stabilizedoxyallylcations derived from epoxidation of chiral allenamides is described here. This intriguing reversal in favor of the endo-II cycloaddition pathway is likely a result of minimizing the dipole interaction between the oxyallylcation and ester carbonyl of methyl 2-fuorate.
Stereoselectivities and Regioselectivities of (4 + 3) Cycloadditions Between Allenamide-Derived Chiral Oxazolidinone-Stabilized Oxyallyls and Furans: Experiment and Theory
作者:Jennifer E. Antoline、Elizabeth H. Krenske、Andrew G. Lohse、K. N. Houk、Richard P. Hsung
DOI:10.1021/ja205700p
日期:2011.9.14
systematic investigation of the regioselectivities and stereoselectivities of (4 + 3) cycloadditions between unsymmetrical furans and a chiral oxazolidinone-substituted oxyallyl is presented. Cycloadditions were performed using an oxyallyl containing a (R)-4-phenyl-2-oxazolidinone auxiliary (2(Ph)), under either thermal or ZnCl(2)-catalyzed conditions. Reactions of 2(Ph) with 2-substituted furans gave